1. Field of the Invention
This invention relates to a magnetometer in which direction of the Earth's magnetic field is determined on the basis of time variant differences in the inductance of a sensor coil of the digital compass which is a function of the orientation of the sensor coil with respect to the Earth's magnetic field. The present invention furthermore refers to a digital compass, in particular for mobile applications, comprising a suchlike magnetometer. It further relates to a novel form of a magnetometer which has general application for determining orientation of weak magnetic fields based on frequency differences, especially for mobile applications, e.g. automotive applications, maritime applications, outdoor activities, airplanes or the like.
2. Description of the Prior Art
A variety of digital compasses and magnetometers are known in the art, e.g. U.S. Pat. Nos. 4,851,775 or 5,239,264.
While the art relating to the design of digital compasses and magnetometers is thus a well-developed one, a need remains for development of a simple, reliable, low cost digital compass suitable for consumer use and a simple magnetometer for determining orientation of low intensity magnetic fields.
Especially, digital compasses according to the prior art generally have the disadvantage that an ASIC (Application Specific Integrated Circuit) is used together with the sensing element, i.e. related to a sensing circuit. This increases the overall cost for the digital circuit.